@Ale-H.H. That is strange....... I cannot think of a good reason for it. There is a click as well, and its as though the osc frequency message has gone instantly to 0 (zero)...... so a fundamental of 8 Hz.
I might be wrong....... there might still be sound there but my crappy mac laptop speakers will not produce it. It could be an overload at very low frequencies.
What does the audio look like in an editor?
Do you see one of the two faders on the module doing something you don't expect?
It sounds really great apart from that!
David.